One form of integrated circuits commonly manufactured uses wire bonding to electrically connect bond pads of a semiconductor die to electrical conductors commonly referred to as traces in a substrate. Integrated circuits therefore typically use uninsulated or bare bond wires that are made of metal such as gold, silver, aluminum or copper. Therefore, the bond wires may electrically short circuit if they come into contact with each other. In order to prevent contact between bond wires, integrated circuits are typically designed such that the bare bond wires do not physically cross or overlap each other. In order to meet this design constraint, the circuitry of the integrated circuit must be designed to keep the bare bond wires from crossing. This design constraint may result in a physical layout that is not optimal for size. Additionally, bare bond wires may sag into other bare bond wires when hot plastic is molded over the integrated circuit assembly. If hot plastic is molded over the integrated circuit, the hot plastic may push the bare bond wires together. To prevent this problem, additional spacing has been included between the bond wire sites.
Additional semiconductor packaging issues must be taken into consideration when using a wire bonding assembly. For example, when either two bond wires or two traces are in close proximity, there is noise coupling commonly found between the two bond wires or two traces. To minimize the negative effects of noise coupling or crosstalk noise, designers commonly separate digital circuitry from analog circuitry. However, this bifurcation often places undesirable design restraints on the design of an integrated circuit and can cause inefficient use of circuit space. When closely positioned adjacent wires or traces exist across a span between an integrated circuit die and a packaging assembly, there is no closely positioned reference plane to minimize the effects of noise from adjacent wires or traces. The noise that gets coupled into the bond wires and traces results in operating error.
An additional source of noise that contributes to error in a semiconductor package using bond wire is from the self inductance of the bond wires and traces themselves. The inductance of the conductor modifies the electrical characteristics of the signal path and therefore the circuit's operation is modified.
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Skilled artisans appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve the understanding of the embodiments of the present invention.